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                         ADAPTIVE BROADBAND CORPORATION

                               SEVERANCE AGREEMENT


THIS SEVERANCE AGREEMENT is entered into as of July 2, 1999 (the "Effective
Date"), between ADAPTIVE BROADBAND CORPORATION, a Delaware corporation ("ADAP")
and George Arena (the "Employee").

                                     RECITAL

The Employee serves as ADAP's Executive Vice President, Operations/Product
Management and Development. ADAP and the Employee desire to set forth the terms
of the Employee's severance compensation if the Employee's employment is ended
as a result of a Change in Control. If a Change in Control occurs, the Employee
and other key employees may be more vulnerable to dismissal or other negative
consequences without regard to the quality of their past or prospective service.
The Board of Directors (the "Board") believes that it is in the best interest of
ADAP and its stockholders to ensure fair treatment to ADAP's key executives and
to reduce any adverse effects upon their performance that may be caused by the
perceived risks of a merger, acquisition or other major structural change.

The parties agree as follows:

1.       DEFINITIONS. For purposes of this Agreement, the following terms will
         have the meanings set forth below.

         1.1      A "CHANGE IN CONTROL" will occur if (a) any Person (as defined
                  in Section 2(a)(2) of the Securities Act of 1933, as amended)
                  other than ADAP, is or becomes the beneficial owner, directly
                  or indirectly (including by holding securities which are
                  exercisable for or convertible into shares of capital stock of
                  ADAP), of 30 % or more of the combined voting power of the
                  outstanding shares of capital stock of ADAP entitled to vote
                  generally in the election of directors ; or, (b) a Transaction
                  is consummated; or, (c) Continuing Directors cease to
                  constitute at least a majority of the Board: or, (d) a
                  majority of the ADAP's Outside Directors determine that a
                  Change in Control has occurred.


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         1.2      "CONTINUING DIRECTORS" shall mean the directors of ADAP in
                  office on January 1, 1999 and any successor to any such
                  director whose nomination or selection was approved by a
                  majority of the directors in office at the time of the
                  director's nomination or selection and who is not an
                  "affiliate" or "associate" (as defined in Rule 12b-2 under the
                  Securities Exchange Act of 1934, as amended) of any person who
                  is the beneficial owner, directly or indirectly (including by
                  holding securities which are exercisable for or convertible
                  into shares of capital stock of ADAP), of 10% or more of the
                  combined voting power of the outstanding shares of capital
                  stock of ADAP entitled to vote generally in the election of
                  directors.

         1.3      "DISABILITY" means that the Employee has met the
                  qualifications for ADAP's long-term disability benefit.

         1.4      "GOOD REASON" includes any of the following:

                  (a)      the assignment to the Employee of duties inconsistent
                           with, or a substantial alteration in the nature or
                           status of, the Employee's responsibilities
                           immediately before a Change in Control;

                  (b)      a reduction in the Employee's salary or other
                           benefits as in effect on the date of a Change in
                           Control;

                  (c)      the Employee's relocation to a work site requiring an
                           increase in one-way commute from Employee's residence
                           of more than thirty-five (35) miles; or

                  (d)      a breach by ADAP of this Agreement if the breach has
                           not been cured within 30 days after written notice by
                           the Employee to ADAP setting forth with specificity
                           the nature of the breach.

         1.5      "OUTSIDE DIRECTOR" is a member of ADAP's Board of Directors
                  who is not, and who during the past six months was not, an
                  employee or officer of ADAP.

         1.6      "TERMINATION FOR CAUSE" is termination of the Employee's
                  employment as a result of (a) the Employee's willful
                  misconduct or the Employee's dishonesty towards, fraud upon,
                  crime against or


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                  deliberate or attempted injury or bad faith action with
                  respect to ADAP; or (b) the Employee's conviction for a
                  felony (whether in connection with ADAP's affairs or
                  otherwise).

         1.7      "TERMINATION UPON A CHANGE IN CONTROL" is (a) termination by
                  the Employee of Employee's employment for Good Reason within
                  one year after the occurrence of a Change in Control; or (b)
                  declination by the Employee of an offer of employment from
                  ADAP, or ADAP's successor, for Good Reason at the time of a
                  Change in Control if the Employee would not have been
                  permitted to remain in Employee's existing position following
                  such declination; or (c) termination by ADAP, or ADAP's
                  successor, of the Employee's employment within one year after
                  the occurrence of a Change in Control other than a Termination
                  for Cause or a termination resulting from the Employee's death
                  or Disability. The one-year period provided for herein shall
                  be six months in the event that a Change in Control arises out
                  of a Transaction defined in Section 1.8 (c) hereof.

         1.8      "TRANSACTION" is (a) a consolidation or merger of ADAP if the
                  shareholders of ADAP immediately before the merger or
                  consolidation do not immediately after the merger or
                  consolidation own equity securities of the surviving or
                  acquiring corporation or a parent party possessing 50% or more
                  of the voting power of the surviving or acquiring corporation
                  or parent party; (b) a sale, lease, exchange or other transfer
                  (in one transaction or a series of related transactions) of
                  50% or more of the assets of ADAP; or (c) the sale or other
                  disposition of business units within any 12-month period that
                  contributed for that 12-month period more than 45% of ADAP's
                  revenues. The Transaction requirements defined in parts (b)
                  and (c) above shall specifically exclude the sale of the
                  Information Systems division and its associated assets, and
                  the designated percentage thresholds for assets and revenues
                  stated herein (50% and 45%, respectively) shall be calculated
                  without including this division's assets or revenues in the
                  base.

2.       TERM. If no Change in Control has occurred, this Agreement will expire
         on December 31, 2000. If a Change in Control occurs prior to December
         31, 2000, this Agreement will continue in effect, and will not
         terminate, until either the Employee has received the severance
         compensation provided for below or has ceased to be eligible for such
         compensation by reason of there not having been a Termination Upon a
         Change in Control.

3.       TERMINATION UPON A CHANGE IN CONTROL. If a Termination Upon a Change in
         Control


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         occurs, the Employee will immediately be paid all (a) accrued
         salary, (b) bonus compensation equal to the higher of (i) the annual
         EIP bonus based on ADAP's operating plan as approved by the Board
         during the first quarter of the fiscal year during which the Change
         in Control occurs, provided that the EVA growth for such fiscal year
         as of the most recently completed fiscal quarter is equal to that
         specified in the operating plan for such period, or (ii) the annual
         bonus or other equivalent incentive compensation payment established
         for the Employee by ADAP's successor and based on the operating plan
         of ADAP's successor at the beginning of the bonus's performance
         period during which Employee's termination occurs, (c) vested
         deferred compensation (other than pension plan or profit sharing
         plan benefits, which will be paid in accordance with the applicable
         plan), unless the Employee is eligible for a delayed payout as
         authorized by the plan, (d) benefits then due under any plans of
         ADAP or ADAP's successor in which the Employee is a participant, (e)
         accrued Personal Time Off pay or vacation pay and (f) reimbursements
         for any appropriate business expenses incurred by the Employee in
         connection with his duties, all to the date of termination ("Accrued
         Compensation"). Repayment of any existing company loans shall be
         extended if necessary to delay repayment until the beginning of
         regular employment during the period of severance compensation
         provided for in Section 4. The Employee will also be entitled to the
         severance compensation described in Section 4.

4.       SEVERANCE COMPENSATION. If a Termination Upon a Change in Control
         occurs, ADAP shall pay monthly severance compensation to the Employee
         for a period ending 24 months after termination, or ending 12 months
         after termination if the Termination Upon a Change in Control (i) is
         initiated by the Employee as specified in Sections 1.7 (a) or 1.7 (b)
         and (ii) is by reason of a Transaction defined in Section 1.8 (c), in
         an aggregate amount determined by adding (a) the Employee's monthly
         base salary at the time of termination and (b) an amount equal to the
         monthly `Perk Pot' benefit to which the Employee was entitled as an
         officer of ADAP at the time of the Change in Control, and (c) the
         amount of $2400.00 in lieu of other employee benefits (including health
         benefits) the Employee was receiving from ADAP at the time of the
         Change in Control. If the Employee begins regular employment prior to
         the expiration of the aforesaid 24 month period, or 12 month period if
         the Termination Upon a Change in Control (i) is initiated by the
         Employee as specified in Sections 1.7 (a) or 1.7 (b) and (ii) is by
         reason of a Transaction defined in Section 1.8 (c), then the severance
         compensation provided for in this Section 4 shall end as of the later
         of (i) the date of such regular employment or (ii) the date which is
         one-half the number of months past he beginning of severance
         compensation provided for in this Section 4. Employee agrees to
         promptly notify ADAP of any such regular employment and to reimburse
         ADAP for any payments made by ADAP hereunder that cover any period
         during which the Employee was a regular employee.

5.       ACCELERATION OF OPTIONS. If a Termination Upon a Change in Control
         occurs, all stock options held by the Employee immediately before the
         termination will become fully vested and the stock options will be
         exercisable for the periods specified with respect to termination of
         employment in the plans covering the options.


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6.       OTHER BENEFITS. Neither this Agreement nor the severance compensation
         that it provides for will reduce any amounts otherwise payable, or in
         any way diminish the Employee's rights as an employee of ADAP, whether
         existing now or hereafter, under any benefit, incentive, retirement,
         stock option, stock bonus or stock purchase plan or under any
         employment agreement or other plan or arrangement, provided, however,
         that the rights granted to the Employee and the obligations assumed by
         ADAP under this Agreement will be in lieu of, and not in addition to,
         any severance or other termination payments to which the Employee may
         be entitled under any employment agreement or other plan or arrangement
         that the Employee may now or hereafter have with ADAP.

7.       EMPLOYMENT STATUS. This Agreement does not constitute a contract of
         employment. It does not impose on ADAP any obligation to retain the
         Employee as an employee, to change the status of the Employee's
         employment or to change ADAP's policies regarding termination of
         employment.

8.       MISCELLANEOUS.

         a.       SEVERABILITY. If a court or other body of competent
                  jurisdiction determines that any provision of this Agreement
                  is invalid or unenforceable, that provision will be adjusted
                  rather than voided, if possible, so that it is enforceable to
                  the maximum extent possible, and all other provisions of the
                  Agreement will be deemed valid and enforceable to the fullest
                  extent possible.

         b.       WITHHOLDING. Compensation and benefits to the Employee under
                  this Agreement will be reduced by all federal, state, local
                  and other withholdings or similar taxes as required by
                  applicable law.

         c.       ARBITRATION. The parties will submit all controversies, claims
                  and matters of difference in any way related to this
                  Agreement, its performance or breach, to arbitration in San
                  Francisco, California, according to the rules and practices of
                  the American Arbitration Association from time to time in
                  effect. Any awards in such arbitration shall be final and
                  binding on all parties. The arbitrators shall allocate the
                  costs of the arbitration in such manner as they deem
                  equitable. The arbitrators may require the reimbursement of
                  all or a portion of the reasonable legal fees incurred by the
                  prevailing party in the arbitration proceeding and any legal
                  proceedings which are taken to enforce the arbitral award.

         d.       ENTIRE AGREEMENT: MODIFICATIONS. (i) This Agreement is the
                  entire agreement between the parties with respect to the
                  matters covered hereby, and may be amended, modified,
                  superseded or canceled, or its terms waived, only by a written
                  instrument executed by each party or, in the case of a waiver,
                  by the


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                  party waiving compliance. (ii) Failure of a party at any
                  time to require performance of any provision of this
                  Agreement will not affect the right at a later time to
                  enforce the same. (iii) No waiver of a breach of this
                  Agreement, whether by conduct or otherwise, in any one or
                  more instances will be construed as a further or continuing
                  waiver of the breach or of any other term of this
                  Agreement. (iv) This Agreement shall inure to the benefit
                  of and be binding upon the successors and assigns of the
                  parties hereto.

         e.       APPLICABLE LAW. This Agreement will be construed under and
                  governed by the laws of the State of California without regard
                  or reference to the rules of conflicts of law that would
                  require the application of the laws of any other jurisdiction.

9.       Prior Severance Agreement. The Employee and ADAP (named "California
         Microwave, Inc." prior to April 29, 1999) acknowledge their prior
         severance agreement dated May 18, 1998. The Employee and ADAP hereby
         terminate such prior severance agreement as of the day immediately
         prior to the Effective Date of this Agreement, and neither the Employee
         nor ADAP shall have any rights or obligations thereunder.


IN WITNESS WHEREOF, the parties have executed this Agreement as of the day and
year first above written.

ADAPTIVE BROADBAND CORPORATION


/s/ Frederick D. Lawrence
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Frederick D. Lawrence                        George Arena
Chairman and Chief Executive Officer         Executive Vice President,
                                             Operations/Product Management and
                                             Development